Two-way flat stroke vibratory conveyors or feeders have substantial applications in a variety of fields. One typical application is in foundry operations wherein, for example, foundry castings may be delivered to a conveyor energized to feed the castings to one end or the other, depending upon where it is desired to locate the castings. Another typical application is in the bulk operations of granular materials wherein, for example, sugar, sand, stone, flour, cement, and various other chemical compounds may be delivered to one end or the other in the same way. Additionally, the conveyors may also move combinations of these object, granular and powder materials.
A conventional two-way flat stroke conveyor made according to the prior-art will typically include a motor powered drive system that includes four drive shafts having pairs of eccentric counterweight wheels connected via an elaborate belt connection. This drive is coupled to an elongated bed with an upwardly facing, generally horizontal conveying or feeding surface terminating at opposite ends. In operation the two sets of eccentric counterweight wheels are driven such that the wheels in each set rotate in opposite direction and the two sets are 90° out of phase relative to one another. When the motor powers the drives, a cyclic vibratory force is produced and the output displacement is transferred to the bed to create material flow. If one were to plot the sum of the stroke versus stroke angle of the sets of eccentric counterweight wheels, the result would be a skewed or biased sine wave in the direction of material flow. By reversing the rotation of the system, the skewed sine wave is reversed and the material flow is reversed.
This prior art conveyor poses a number of problems, the greatest of which is the complexity of the drive on what is essentially a brute force system. In other words, as the drive consists of four shafts with pairs of eccentric counterweight wheels, and the wheels, bearings and shafts must be large to transfer the forces, the result is a complex belt drive system with great maintenance and alignment difficulties.
U.S. Pat. No. 5,934,446 to Thomson (incorporated herein by reference) attempts to address these problems with a vibratory conveyor that includes a generally horizontal, elongated conveying surface connected to a base by generally vertically arranged, resilient slats. A drive is mounted to the surface and includes two rotary eccentric shafts coupled in series and set 90° out of phase for vibrating the surface in a generally horizontal direction by imparting a cyclic vibrating force in the form of a skewed sine wave. In other words, the drive, through the connecting drive slats, imparts a horizontal force to the trough, causing it to vibrate in the horizontal direction.
Essentially, the conveyor in the Thomson patent is tuned, through the reactor slats, to approximately 7% above the primary shaft rpm. This design, as such, takes advantage of the sub-resonant natural frequency and reduces the forces to the drive bearings as well as reducing the motor size requirements as compared to the prior art. In other words, the primary horizontal eccentric force and stroke is amplified and the lessor secondary eccentric wheel force is transmitted in a brute force manner, resulting in a smaller skewing stroke component. However, the disadvantage of the Thomson patent remains its drive complexity and space limitation with respect to both manufacture and maintenance costs.
Accordingly, it is a general object of the present invention to provide a new and improved flat stroke bi-directional conveyor.
Another general object of the present invention is to overcome those deficiencies of the flat stroke conveyors of the prior art.
It is a more specific object of the present invention to provide an improved flat stroke bi-directional conveyor which utilizes the skewed sine wave principle to transfer force to the conveying bed.
It is another object of the present invention to provide an improved conveyor which utilizes less and smaller component parts, as compared to current practice, thereby greatly reducing manufacture and maintenance costs.